Electric-hydraulic flap control system



June 25, 1956 H. E. METCALF ELECTRIC-HYDRAULIC FLAP CONTROL SYSTEM Filed April 17. 1955 sig-i mlvf @w j Nm. mm.

United States Patent ELECTRIC-HYDRAULIC FLAI coN'rRoL SYSTEM Herbert E. Metcalf, Los Angeles, Calif., assignor to Northrop Aircraft, Inc., Hawthorne, Calif., a corporation of California Application April 17, 1953, Serial No. 349,508

6 Claims. (Cl. dll-S2) This inventionrelates toV ahydraulic control system of general utility and more particularly to a hydraulic system useful for actuating control surfaces of airplanes.

In certain types of aircraft it has been found desirable to provide certain surfaces that are only occasionally used, such as landing flaps and dive brakes, with exact hydraulic positioning control. Hydraulic control requires the use of fluid under pressure, and when-the control surface is not often operated, it is neither necessary nor desirable to consume power to maintain a constant supply of hydraulic uid under pressure in the airplane, particularly when no other use for such fluid is present.

It is an object of the present invention to provide means for actuating surfaces such as the landing aps or dive brakes'of an airplane in which the source of power for said means functions only during periods in which the surfaces are being moved.

Another object is to provide means whereby the position a power actuated ilap will assume is exactly predetermined by the priorY setting of the pilots landing ap control unit.

Brielly the present invention in one form as practiced includes the use, in an airplane control system, of ahydraulic cylinder-piston type motor connected to move a control surface of an airplane by movement of a fluid control valve as controlled by the pilot of the airplane. A follow-up system is provided so that the motor-will move the surface to a position exactly in accord with the position to which the valve has been moved.

As the valve movement is started, a power means is 'automatically energized to supply hydraulic fluid under pressure to the hydraulic motor, the power means then beingautomatically tie-energized as surface movement ceases. In this manner the surface is exactly positioned and power isconsumed only while the surface is being moved.

The invention will be more clearly understood by detailed reference to the accompanying drawings Vin which:

Figure 1 is a diagrammatic view of an airplane landing flap control system embodying the present invention.

Figure 2 is a diagrammatic sectional view of a hydraulic motor and control valve suitable for usev in the present invention.

Referring rst to Figure 1, a landing flap 1 is mounted for rotary movement about an axis 2, the ap 1 being supported by suitable bearings (not shown) attached to an airplane wing 3. The landing llap 1 is moved by a hydraulic motor or actuator 4 preferably of the neutral leakage type which is disclosed for example in U. S. Patent No. 2,612,872 (Strayer).

As diagrammatically shown in Figure 2, a hydraulic motor or actuator 4 comprises a hydraulic cylinder 5 and servo valve 6, the cylinder being provided with a conventional piston rod 7 and piston 7a, and the valve being provided with a valve stem 8 and spool 8a for directing uid to the desired end of the hydraulic cylinder through bores 8b as they are uncovered by spool move- 2,751,752 Patented June 26', 1956 ment. Spool movement in this type of valve is on the order of only two-tenths of? an inch in either direction from neutral for full power application. The closed end of cylinder 5 is attached to the nose portion of the ap 1 by means of a pin 9 positioned in spaced relation with respect to axis 2. The end of piston rod 7, extending from the hydraulic cylinder 5, is attached to a bearing support 10 by means-of a pin 11, the bearing support 1i) being secured, as by Welding, to a structural elementfof the Wing 3. Also rotatably mounted on pin 11 is a cable quadrant 12` to which-the valve stem 8 is attached through a connecting link- 13; the attaching point of the link being located radially outward of pin 11. A pair of ilexible cables 14 and. 15 extend from the quadrant i2 to acable pulley 29; theA construction and functionithereot' being described later. The cables 14 and 15 are secured to the quadrant 12 and pulley 29 in a conventional manner` with the cables beingpositioned by means of a pair of idler pulleys 16.

Fluid 17 for the hydraulic. actuator is supplied to motor 4 from a reservoir 18 throughY a pressure conduit 19 and returned to the reservoir via return conduit 20.. A hydraulic constant pressure pump 21 and'check valve 22 are positioned in pressure conduit. 19. rThe check valve, being located adjacent servo valve 6, permits uid flow tothe valve 6 but check'sfluid from flowing in a reverse direction. An-v elecnically operated solenoid valve 19a, normally closed, is positioned. in conduit 2t). An electricmotor 23, so connected; that it is energized and deenergized in accordance with. the operation of a landing ap. control unit 25 in a manner to bepresently described, actuates hydraulic pump 21 by means of a conventional drive as indicated by broken line 24.

The pilots landing flap control unit 25 is mounted in the cockpit of the airplane (not shown) with which it is associated, the same being further located so that it is readily accessible by the pilot. Unit 25 comprises a control handle 26, an outer drive lever 27, an inner drive lever 28 and the cable pulley 29, all rotatably and independently mounted sideby side onV a mounting pin 36. A torsion spring 31 is also centrally positioned about mounting pin 30 between the inner drive lever 23 and the'cable pulley 29. The inner end'of spring31 is attached to the inner drive lever 2S While its outer end is attached to the outer drive lever 27 near its outer end,

the Spring 31 being preloaded by a'predetermined amount.

of wind-up to tend to force the drive, levers 27 andy 28 toward each other.

In the rest position of the flap control unit 25, the outer ends of both drive levers 27 and 23 are held apart against the rotative forceof the -preloaded spring 31 by a pulley pin 32 which is iixed to pulley 29. Since both drive levers 27 and 2S arebearing against pulley pin 32,.one on each side thereof, no resultantforce is normally exerted on the cable pulley 29 to rotate it about theV mounting pin 39. v

A lower extension 34 of the control handle 26l is provided with a pin 35 which also extends between the drive lever ends, the pin 35 functions to rotate one of the drive levers 27 or 28 depending upon which direction the control handle 26 is moved. Control handle 26. -is mounted sothat it cannot bemoved by the forcev exerted by spring 31.

Thus if either the outer or inner lever 27 lor 23' respectively is displaced in the direction away from the pulley arm pin 32 by operation of handle 26, thepower stored in spring 31 acting on the other lever and pin 32 rotates the cable pulley 29 in the sameV direction as the initial drive lever. was displaced. As the cable pulley 29 is free to turn on pin 30 it will reach a new neutral or rest position when the-pulleyarm pin 32 again contacts the end of the drive lever which was displaced.

An accurate scale'element 49, the same being nonmovable, is positioned adjacent the control handle 26. The scale element 49, preferably graduated in degrees, cooperates with an index element 50 located on the control handle 26 to indicate thel relative position of the Ycontrol handle with respect' to the scale 49. The position of index element 50 relative to the scale 49 also indicates the position which the ap 1 will automatically assume. The energization of motor 23 is controlled by a pair of spaced switches 60 mounted on a bracket 60a extended from valve 6, these switches 60 being positioned parallel to and at one side of valve stem 8. Mounted on valve stem 8 to move longitudinally therewith is a linear cam 61, positioned between operating arms 63 of the two switches 66 so that when the valve spool 8a is in the neutral position both switches 60 are open circuited and so that when relative movement between valve stem 8 and the housing of actuator 4 occurs, one or the other of the switches 60 is closed.

Switches 60 are connected in parallel electrically and then through a relay battery 65, a switch 66 to a power relay 67. Power relay 67 controls power from power mains 68 to motor 23 through power line 69. Power line 69 is also connected to solenoid valve 19a through solenoid line 70.

In operation, the pilot moves the handle 26 to change the position of ap 1. Rotation of cable pulley 29 occurs with this movement until the resultant movement of the valve stem'8 causes spool 8a to bottom in valve 6. During this initial movement one of the switches 60 is closed, thereby starting motor 23 which drives pump 21. The hydraulic motor 4 then acts to move the surface 1 Vto cause the valve 6 and cylinder 5 to follow the valve stem 8. However, when handle. 26 is moved past the point where the spool 8a has bottomed, the cable pulley `29 cannot rotate any Vfurther and spring 31.is accordingly Ywound up. The handle 26 is frictionally mounted so that it can readily be moved by the pilot, but resists being Y moved by the maximum force that can be exerted by spring 31. Then, as the valve 6 moves, the spring 31 will rotate the cable pulley 29 to keep the valve stem 8 ahead of the valve until spring 31 no longer acts on cable pulley 29, thereby establishing a valve stem position corresponding to the handle position. Valve 6 and cylinder 5 (and the attached surface) continue to move until valve spool neutral is reached, at which time the closed switch is opened, and the motor 23 ceases to actuate pump 21.` v

At such times as the motor 23 is energized the solenoid valve 19a is open allowing fluid flow through the return conduit 20. With the motor 23 de-energized the valve 19a is closed thereby arresting uid flow through the return conduit. Under certain conditions the spool 8a functions, in cooperation with the check valve 22, to provide a hydraulic lock in the actuator 4. This hydraulic lock occurs at such times as the actuator 4 is moved slightly, as'a result of pivotal movement-of the-flap 1,

which movement in turn causes the spool 8a toV move Yslightly from its neutral position in its housing. Accordingly the above hydraulic lock acts to maintain the flap 1 in a substantially desired position regardless of air loads acting on the Hap.

The action of the valve 6 provides very accurate positioning Vfor the flap 1 and the connections described cause the ap 1 position to accurately coincide with the position to which the handle 26 is moved by the pilot.

Thus it is seen that the pilot may place the control handle 26 in any position desired; the ap 1 automatically assuming its correct relative position without further attention. l

While a preferred embodiment of the present invention has been shown and described in connection with a landing flap associated with an airplane, it will be clear to -those skilled in the art that it may be utilized to actuate any of the control surfaces of an airplane Vthat are relatively occasionally utilized. Also the invention may be utilized to move any surface or structure not necessarily associated with an airplane, to a predetermined position in accordance with the pre-positioning of the control unit.

While in order to complywith the statute, the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specilic features shown, but that the means and construction herein vdisclosed comprise a preferred form ofV several modesV of puttingthe invention into eiect, and therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

What is claimed is:

l. In an airplane having a controlk surface, a device for moving said control surface to a predetermined position comprising: a hydraulic actuator comprising a servo valve and a-cylinder mounted to move said surface, said valve having a neutral position in which no fluid flows to said actuator to effect movement of said control surface, a source of hydraulic fluid, conduits providingV supply and return lines between said source and saidVV actuator, a pump in said supply line adapted to supply uid at super-atmospheric pressure, a check Yvalve in said supply line positioned between said pump and said servo valve, a motor for driving said pump, a manual control element mounted forV rotary movement, said control element and control surface having rest' positions Yat such time as said valve is in said neutral positionasaid control elementand control surface having predetermined corresponding positions with respect to each other when in said rest positions, cable meansk connected between said control element and said servo valve for `actuating said Servo valve in response to movements of saidrcontrol element, and electrical switch means operated by relative movement of said servo valverand said cylinder Ywhereby said motor is energized when said control element and control surface are not in said rest positions and is de-energized when said element and surface are servo valve, piston cylinder, piston, and housing, attached to said primary and secondary structures and being adapted to angularly move the latter structure; a source of hydraulic fluid; hydraulic supply-and return lines extending between said source and actuator; a pump yin said supply line; a motor for driving said pumpgnsaid valve having a neutral position and non-neutral positions with respectY tosaid housing inV which lluid does not ow and uid flows, respectively, to said piston cylinder to effect movement of said secondary structure; the mounting of said actuator providing follow-up means whereby said valve isA returned from said non-neutral positions to said neutral position Vby movement'of said secondary structure; electrical switch meansY operatively connectedwith Ysaid motor and being responsive to positions of said valve so that said motor, is Yde-energized or energized when said valve is in said neutral or non-'neutral positions, respectively; a control element Ypivotally mounted on said primary structure; and cable means connected between said control element and valveV whereby the latter may be moved from its neutral position.

3. Apparatus as set forth inclairn 2,; in which lthe saidfollow up means is further characterized by said piston being pivotallyattached .to4 said primary structure and said housing being pivotally attached to said Vsecondary structure at a position'spaced from the pivotal axis set forth Vinfclaini further 'characl terized in that said secondary structure automatically assumes a predetermined angular position according to the angular position of said control element.

5. Apparatus as set forth in claim 2: further characterized in that said valve allows each end of said piston cylinder to be subjected to fluid at super-atmospheric pressure at such time as said valve is in said neutral position; a check valve in said supply line between said pump and said servo valve; said check valve permitting unidirectional flow to said actuator; an electrically operated valve in said return line being opened or closed in accordance with energization or deenergization, respectively, of said motor; said servo, check, and electrically operated valves cooperating to provide a hydraulic lock in said piston cylinder at such times as said housing is moved, with respect to said servo valve, due to pivotal movement of said secondary structure with respect to said primary structure.

6. Apparatus for electing predetermined angular movements of a structure, comprising: a primary structure; a secondary structure pivotally mounted on said primary structure; a unitary hydraulic actuator, comprising a servo valve, piston cylinder, piston, and housing, attached to said primary and secondary structures and being adapted to angularly move the latter structure; a source of hydraulic fluid; hydraulic supply and return lines extending between said source and actuator; a pump in said supply line; a motor for driving said pump; said valve having a neutral position and non-neutral positions with respect to said housing in which uid does not ow and uid flows, respectively, to said piston cylinder to eiect movement of said secondary structure; the mounting of said actuator providing follow-up means whereby said valve is returned from said non-neutral positions to said neutral position by movement of said secondary structure; electrical switch means operatively connected with said motor and being responsive to positions of said valve so that said motor is de-energized or energized when said valve is in said neutral or non-neutral positions, respectively; a control element, including a pair of follow-up drive members, pivotally mounted on said primary structure for movement through an angular range; and cable means transmitting movements of said control element and drive members to said servo valve causing said secondary structure to assume a different predetermined angular position With respect to said primary structure for each angular position of said control element throughout said angular range.

References Cited in the tile of this patent UNITED STATES PATENTS 2,120,495 Harris June 14, 1938 2,132,325 Soldatti Oct. 4, 1938 2,387,307 Stone Oct. 23, 1945 2,395,671 Kleinhans et a1 Feb. 26, 1946 2,596,242 Hill May 13, 1952 

